Recently, a hybrid vehicle that can operate using electrical power has been actively developed. The hybrid vehicle is equipped with a battery charged with power, and uses the power charged in the battery at the time of operation. Such a hybrid vehicle improves power performance and decreases gas mileage based on an algorithm of operating a motor and an engine depending on the SOC of a high voltage battery.
FIG. 1 is a diagram showing a case where the SOC calculated by the battery controller of a hybrid vehicle is continuously within a range of ±5% of a base SOC at the time of normal urban driving. The SOC is calculated using the following Equation
                              soc          ⁡                      [            n            ]                          =                              soc            ⁡                          [                              n                -                1                            ]                                -                                                                      ∑                                      n                    -                    1                                    n                                ⁢                I                            Ah_basic                        ⨯                          100              ⁡                              [                %                ]                                                                        (        1        )            wherein SOC is the state of charge, I is the charged/discharged current of the battery, and Ah_basic is the reference capacity (rated capacity).
However, as illustrated in FIG. 1, in the case where the hybrid vehicle continuously repeats a normal urban driving mode, the battery experiences a memory effect, so that 100% of the rated capacity of the battery may not be used. That is, if the SOC is continuously within a range of ±5% of the base SOC, a problem occurs in that the maximum capacity of the battery decreases, thereby shortening the lifetime of the battery.